In this paper, surface modification of cerussite by thermochemical processing with pyrite was studied based on microflotation tests, X-ray powder diffractometry (XRD), X-ray photoelectron spectroscopy (XPS) and electron probe microanalysis (EPMA). Microflotation test results showed that the surface modification facilitated flotation of the treated cerussite and improved the flotation recovery to approximately 90%. The results of XRD analyses confirmed that cerussite was transformed into massicot, which then interacted with pyrite to form PbS, PbSO4, PbO·PbSO4 and 4PbO·PbSO4. XPS analyses results revealed that both PbS and PbS2 were formed on the mineral surface, and the percentage of PbS increased with increasing FeS2/PbCO3 (F/P) mole ratio, which was advantageous for the flotation of the modified cerussite. EPMA analyses showed that particles with layered configurations were obviously formed after thermochemical processing. The thickness of the products at the outer layer of the particles increased when the F/P mole ratio increased. Moreover, the S and O contents in the products increased and decreased, respectively.